Duke Energy Corp. started permanently filling the first of 23 floors in its new corporate headquarters in uptown Charlotte last weekend, moving human-resources, legal and finance workers into the 38th floor.

The employees will use ergonomically designed desks and chairs in work spaces outfitted to cut down on airborne irritants and maximize natural sunlight over artificial lighting.

Recycled materials are used wherever possible throughout the new offices, says Dennis Wood, Duke’s vice president of real estate services. The wallboard on every floor was manufactured by Charlotte’s National Gypsum Co. at Mount Holly, using gypsum produced from Duke’s coal-burning plants.

Kay Gilreath led visitors on a tour of the 22nd floor Wednesday. A couple of dozen workers from various departments have been working in temporary assignments on that floor since April, giving Duke a chance to see if the new design features proved as effective as hoped. The pilot has worked out well, with some changes being made to accommodate the workers after they moved.

Brooke Whalen, who works in human resources, says it has all worked perfectly. “It’s like moving to an upgraded home for free,” she says.

She’s especially pleased with the natural lighting, although she admits she’s also happy that the vending machine on her floor has a much wider selection than in the old headquarters at 526 S. Church St.

The 48-story Duke Energy Center at 550 S. Tryon St. is arguably the greenest skyscraper in the United States. It was started by Wachovia Corp. for its own corporate headquarters and finished by Wells Fargo & Co. after the San Francisco-based bank (NYSE:WFC) bought Wachovia. The building has earned the a platinum certification under LEED construction guidelines — the highest rating available for environmentally sound construction.

Wood says the high standards used in the basic structure give Charlotte-based Duke (NYSE:DUK) a big leg-up on its goal of earning platinum certification for its interior designs. Lease agreements in the building require tenants to achieve at least a gold LEED rating. Duke wants to do better.

The insulation in the walls was made from recycled denim fabric. The table surfaces in the “cafés” (“Don’t call them break rooms,” Gilreath says) are reprocessed polyester. Overall, more than 30 percent of the furnishings are made from recycled materials. There are low-flow restroom fixtures and waterless urinals to conserve water.

Duke has separate monitoring of the energy use for each of its floors. Electronic displays in each café show real-time use levels for lights, receptacles and heating and air conditioning. “We will display how each floor is doing compared to other floors,” Wood says. “We hope to get a little competitive spirit going.”

Altogether, the new offices are projected to be about 20 percent more energy efficient than space not built to the LEED standards.

And Duke has another project under way in the new headquarters. The company is designing what it calls the Workplace of the Future.

If the LEED standards set out to provide maximum sustainability and minimum environmental impact on each floor, the workplace initiative is designed to provide the best working conditions. The desks have adjustable heights. Computer screens can all be brought to eye level for any worker, at whatever angle the employee finds most comfortable. There are work stations in groups of four set up for cooperative work. Additional private stations in the open floor plan are designed for what Duke calls “heads-down” work.

Spaces have been designed for engineers. There are large conference rooms for meetings and small “enclaves” where two to four employees can collaborate.

Workers from out of town can use secure lockers to store their personal belongings while they work in the office. Informal work stations of various types line the windows on the outside walls.

“We are trying to create more collaborative and friendly environment to help our employees as productive as they can be,” Wood says.

And there are rooms on every floor dedicated for personal health use. Gilreath says a nursing mother who might need to pump breast milk or a diabetic who must inject insulin can use the rooms for privacy.

Duke is already implementing the same design principles at upgrades to its Fourth and Main annex in Cincinnati and the Cherokee Operations building in Whittier, N.C.